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Plantar pressure changes with customised and prefabricated orthoses

Discussion in 'Biomechanics, Sports and Foot orthoses' started by JFAR, Jun 17, 2009.

  1. JFAR

    JFAR Active Member


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    Contoured, prefabricated foot orthoses demonstrate comparable mechanical properties to contoured, customised foot orthoses: a plantar pressure study

    Anthony C Redmond, Karl B Landorf, Anne-Maree Keenan

    Journal of Foot and Ankle Research 2009, 2:20

    Background
    Foot orthoses have been demonstrated to be effective in the management of a range of conditions, but there is debate as to the benefits of customised foot orthoses over less expensive, prefabricated devices.

    Methods
    In a randomised, cross-over trial, 15 flat-footed participants aged between 18 and 45 years were provided with semi-rigid, customised orthoses and semi-rigid, contoured, prefabricated orthoses. Pressures and forces were measured using an in-shoe system with subjects wearing shoes alone, wearing customised orthoses, and again when wearing contoured prefabricated orthoses. Two weeks acclimatisation was included between cross-over of therapy. Repeated measures ANOVA models with post-hoc, pair-wise comparisons were used to test for differences.

    Results
    When compared to wearing shoes alone, wearing either the customised orthoses or the prefabricated orthoses was associated with increases in force and force time integrals in the midfoot region. Peak and maximum mean pressure and pressure-time, and force-time integrals were reduced in both the medial and lateral forefoot. There were, however, no significant differences between the customised orthoses and the prefabricated orthoses at any site.

    Conclusions
    There was a similar change in loading with both the semi-rigid customised and the semi-rigid prefabricated orthoses when compared to the shoe alone condition. While customised devices offered minor differences over prefabricated orthoses in some variables, these were not statistically significant. The results suggest that there may be only minor differences in the effects on plantar loading between the customised and the less expensive prefabricated orthoses tested in this study. Further research is warranted.
     
  2. Im just wondering what they mean by customised foot orthtoics. Did each patient get the same type of device which has been made from a casting and therefore custom, or did they really get custom orthtoics where each device was made differently for the foot requirements.

    If they got the same type of device Im not sure you can call it custom.

    Also which type of devices were used.

    Maybe I will have to wait for the full text which was not available yet.

    Michael Weber
     
  3. Griff

    Griff Moderator

    Michael,

    Full text is available - on JFAR website

    Attached for you

    Ian
     

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    Last edited: Jun 17, 2009
  4. Thánks Ian Ive quickly read it.

    Hopefully it will lead to a study which includes more individual custom orthtics, different and more up to date orthotic prescriptions.

    Also when they discuss cost they dont mention the lenght of time that a device will last for, the non "custom" maybe cheaper at the beginning but as you replace it more often it tends to be more expensive in the end I find.

    Just my option

    Michael Weber
     
  5. Good points Michael

    I think a clear distinction needs to be made between custom casted and truly custom orthotics. The method used in many studies of this type is a device casted to a root protocol. We might say that this study shows no significant kinematic differences between a neutrally casted and balanced orthotic and the pre fab. Other studies have shown similar results.

    When comparing two types of orthotic (such as custom casted and pre fab) it is important not to forget that we are doing simply that. We are not comparing a type against a baseline because no baseline exists. This study indicates that a neutral cast has a similar effect to that type of pre fab (initially) It offers no information regarding the comparison of, say, a pre fab and a casted device with an intrinsic forefoot post and a reverse mortons extension.

    These studies are often used, wrongly, to imply that there is no need for custom orthotics because the outcomes are no better than with pre fabs. They do not prove this any more than a similarity between outcomes of co codamol and paracetamol would abrogate the need to visit one's GP for migraine. The GP MIGHT use either one of these, or he might use something different altogether. One might consider removing co codamol or paracetamol from that gp's toolkit on the strength of that trial but one would certainly not challenge the need for a "customized" treatment plan based on a full assessment.

    And who knows? Perhaps the GP has subject specific data lost on the trial, that people with blond hair do better with paracetamol whereas bald people do better with co codamol. These variables can be lost in large statistical samples.

    These studies should only feel threatening to clinicians who do not have more than one prescription for custom casted devices in their toolkit. There are plenty of these around, who take a history they do not examine, scan the foot, send it to a lab, and get their "customised" orthoses the next week.

    Kind regards
    Robert
     
  6. David Smith

    David Smith Well-Known Member

    All

    I thought much along the same lines as Robert but from a different perspective.

    In many cases where custom and OTC orthoses are compared the target is set and the researchers find that both can hit it and perhaps with with similar regularity and accuracy. However the target set was one which both were able to hit.

    Example: Target = pressure changes in a certain area of the plantar foot. In the experiment the pressure under the 1st MPJ is the same or changes by the same amount for both types of orthosis.

    However in one the 1st ray stabilised in a dorsiflexed position and in the other it stabilised in a relatively mor plantarflexed position.

    Both hit the required target but the other target of 1st ray position was not considered and so goes unremarked upon.

    The second thought is statistical versus clinical significance in terms of the requirements of the appliance for the purposes of the job.

    Question can Gazelles run faster than Lions?

    E.G. In observing lions chasing gazelle it was observed that when recording the speed of lions and gazelles during the chase there was no significant difference in speed between the two. However very significant for the Gazelles was that they were seldom caught. The reason is that although they were capable of running much faster than the lions, gazelles always had a small head start in the chase and only needed to match the lions speed to maintain the distance.

    They did what was required for the job in hand and the result was highly significant in terms of survival but wholly insignificant in terms of difference in speed.

    Just mulling over some thoughts,

    Cheers Dave
     
  7. If my goal was to show that "expensive" custom-casted prescription foot orthoses were no better than "less-expensive" over-the-counter foot orthoses, then I would design my foot orthosis study almost exactly as this one:

    1. Use a flat-footed population.
    2. Use no specific orthosis modifications that are routinely used to treat flat-footed patients (i.e. no medial heel skive, no Blake inverted modification, no DC inverted wedge was used in this study).

    The results of this pressure-mapping orthosis study would have been totally different if the authors had used a cavus foot population, as Josh Burns and coworkers have already shown (Burns J, Crosbie J, Ouvrier R, Hunt A: Effective orthotic therapy for the painful cavus foot. JAPMA, 96:205-211, 2006) or had used orthosis modifications that are widely and commonly used by the podiatric profession for treating pronation-related symptoms (e.g. medial heel skive, Blake inverted orthosis, DC inverted wedge).
     
  8. efuller

    efuller MVP

    I agree with the comments above in criticism of the study. The study appears to be done by someone who just got a pressure sensing machine and realized that variables that can be measured are pressure, pressure time integral etc. Then they decided to measure those variables without thinking what their measurements mean. If the piece of plastic contacts the arch, some of ground reaction force will be applied there. Total force should not change so if force increased in one location it should decrease in another. Of course this will also affect the force time integral and the pressure time integral as well.

    The orthotic is only a peice of plastic. If I were to make a prefabricated device the shape I would choose would be one that matched an average of the custom made devices. Some prefabs even come with intrinsic forefoot valgus post and a heel cup that looks like a medial heel skive. So, if your custom device was of average arch height and included those prescription variables then I really would not expect much difference in shape of the device or any observable parameter, including patient comfort. However, if you added a top cover and a reverse Morton's extension then I would expect a difference even if you used the same shell.

    We have to remember that the piece of plastic that the patient stands on works because its shape changes the forces applied by the ground. A custom device does not work because of the postion that the foot was casted in. If there is no difference in the shape of the custom device from the OTC device then we should not expect them to be different. However, as has been pointed out, prescription variables can make a difference. (Heel skive, reverse Morton's extension) We earn our money when we choose the correct custom modifications or know when to tell the patient that the custom device won't be much better than the OTC device.

    Regards,

    Eric Fuller
     
  9. LuckyLisfranc

    LuckyLisfranc Well-Known Member

    Dear all

    This seems to be another in a growing line of study protocols that could be perceived to be designed to say prove all orthoses are equal, and custom devices are just expensive and unneccessary. I can understand the rationale that a few rotten apples exploit the situation for economic gain by using custom devices when a prefab would do, but this is a dangerous trend.

    It disturbs me: firstly, because of the criticisms of the study design mentioned by others on this thread. Secondary, because it appears to add to a pile of studies that seem to be very antagonistic towards custom devices - is there a growing observer bias creeping into academic podiatry research into orthotics?

    The third most important issue is to be careful what you wish for...if studies like this have an (intentional or unintentional) consequence of raising enough doubts about the appropriateness of custom devices, then heaven help the patients when health insurers stop paying. Wither podiatry, pedorthics, P&O and the custom device?

    There are much more useful and pressing research answers we are in need of.

    LL
     
  10. DaVinci

    DaVinci Well-Known Member

    I finally got to read this and I just don't get it.

    They compared a prefabricated orthotic with a custom made. If they had more or less arch full on the custom made device they would have got a totally different result.

    I also don't get why they used "pressure" - since when is that important in the working of a foot orthotic (unless it a foot orthotic designed to change pressure such as offloading the diabetic foot)

    The results and research are meaningless.
     
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